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ABSTRACT: The solar flare of 28 October 2003 (X17.2/4B) was recorded by the SONG instrument onboard the CORONAS-F satellite. Adescription
of the SONG instrument, its in-orbit operation and the principal data reduction methods used to derive the flare gamma-ray
properties are presented. Appreciable gamma-ray emission was observed in the 0.2 – 300MeV energy range. Several time intervals
were identified which showed major changes in the intensity and spectral shape of the flare gamma-ray emission. The primary
bremsstrahlung proves to be extended to 90MeV and dominates during 11:02:11 – 11:03:50 UT time interval, i.e. at the beginning of the flare impulsive phase. Afterwards, the SONG response was consistent with detection of the pion-decay
gamma emission. Asharp increase in the pion-decay-generated gamma-ray emission was observed at 11:03:51±2s UT, implying
a substantial change in the spectrum of accelerated ions, which testified the appearance of protons with energies of >300MeV
on the Sun. This emission lasted at least 8 – 9min until the end of our measurements. The ion acceleration to high energies
was also proved by the detection of neutrons with energies >500MeV. It was found that the most efficient acceleration of
high-energy protons coincides in time with the highest rate of the magnetic-flux change rate. The maximum gamma-ray flux at
100MeV was 1.1×10−2photons cm−2 s−1 MeV−1, exceeding all the fluxes that have ever been recorded.
Solar Physics 04/2012; 268(1):175-193. · 2.78 Impact Factor
